From bug-octave-request at bevo dot che dot wisc dot edu  Mon Dec 13 23:25:04 1999
Subject: bug in loading files with global vars and in "global x = y"
From: stevenj at gil-galad dot mit dot edu
To: bug-octave at bevo dot che dot wisc dot edu
Date: Mon, 13 Dec 1999 23:25:49 -0600 (CST)


Dear Octave Maintainers,

I have found a bug in Octave's handling of global variables.  (This bug
manifests itself in the latest CVS snapshot.)  First of all, the construct
"global x = y" doesn't work:

octave> global g = "should be global"
octave> is_global("g")
ans = 0

You have to declare it as global separately, after it has been assigned a
value:

octave> global g
octave> is_global("g")
ans = 1

A similar problem manifests itself in saving/loading the variables:

octave> save "g.save" 

Note that octave's native file format(s) save whether or not a variable is
global.  Now, if we quit Octave and start it again, we get:

octave:1> load "g.save"
octave:2> is_global("g")
ans = 0

However, if we load a second time (with -force) it works:

octave:3> load -force "g.save"
octave:4> is_global("g")
ans = 1

So, it seems that the bug is that both the load command and "global x = y"
try to set a variable as global before it is defined, and that doesn't
work.  Setting an already-defined variable as global works.

(I looked at the source code for load, and it certainly looks like it is
trying to set the variable as global before assigning it a value.  I
assume that this worked at some point, so presumably something has
changed about Octave's symbol table to break this behavior.)

Cordially,
Steven G. Johnson



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